The tread of a tire may be equipped with one more structural features for the purpose of e.g., improving traction and/or rolling resistance performance over a variety of different conditions. For example, grooves, incisions, and other elements may be formed into the tread. The orientation of such features may be specifically determined to provide certain performance characteristics.
Traction performance is not determined solely by such structural features, however. The composition of the materials used to manufacture the tread can also affect traction performance, rolling resistance, or both. Such is particularly true with ultra-high performance (UHP) tires such as racing tires that may be used during relatively high speed and high torque conditions.
For example, relatively softer rubber compositions (i.e. having a lower elastic modulus and/or lower Shore Hardness) have been developed that can provide higher grip under UHP conditions. Unfortunately, such softer rubber compositions also wear quickly. Decreasing the softness of the rubber compositions can improve wear but a trade-off occurs because generally such decrease will also result in less grip. Accordingly, some conventional constructions have proposed rubber compositions that attempt to compromise this trade-off over the useful life of the tread but sacrifices are necessarily made to either grip, wear, or both.
Constructions have also been proposed for non-UHP tires that utilize different rubber compositions within the tread over its useful life. Such have been proposed, for example, to improve wet traction as the tread wears over its useful life and thereby reduces the depth of grooves and channels otherwise available to evacuate water from the contact patch. The tread is designed so that as it wears and the tread depth decreases, the contact surface of the tire is increasingly formed by a relatively softer rubber composition that provides increased wet traction. Unfortunately, for UHP applications, such use of softer, higher grip compositions at a deeper tread depth can lead to blistering and other problems that negatively affect performance as the temperature of the tread increases during use.
Accordingly, a tire that can provide improved grip and wear performance particularly in UHP applications would be useful.